1. Field of the Invention
The embodiments of this invention generally relate to the synthesis of nanoscale objects, and more particularly to the synthesis of nanoparticles.
2. Description of the Related Art
Nanoscale objects with size of several hundred nanometers or less have promising potential in optic, electronic, magnetic, and catalytic applications. Progression in the production of monodisperse noble metal (Au, Ag, Pt and Pd), semiconducting, and magnetic nanoparticles has provided various systems suitable for nanooptic, nanoelectronic and nanomagnetic studies in mapping the scaling limits of future information technology, understanding spin-dependent transport phenomena, and using nanoparticles as highly sensitive labels (both magnetic and optic) for bio-recognition.
U.S. Pat. Nos. 6,123,920 and 6,203,777, the complete disclosures of which, in their entireties, are herein incorporated by reference, have suggested that nanoparticles with diameters smaller than 20 nm are ideal for biomedical applications. These small nanoparticles can in principle allow only one or several biomolecules, especially DNA strands, to attach and may be used as easily identified labels for future highly sensitive biomolecule separation and detection. Additionally, noble metal nanoparticles, especially Au nanoparticles, can be used for site-specific attachment of biomolecules, such as DNA strands, by using the high affinity of Au to a thiol group (SH). Furthermore, Au nanoparticles in a variety of size ranges have been synthesized and used for thiol-terminated biomolecule attachment, facilitating optic detection of the biomolecule via surface plasmon property of the Au nanoparticles. An alternative, yet a potentially more sensitive, approach involves using magnetic nanoparticles as tagging labels. The tagged biomolecules can be enriched, separated, or detected magnetically.
One recent research push has been in making nanoparticle labels with core/shell type structure with the core being a magnet and the shell being Au as described by Lin, J. et al, “Gold-Coated Iron (Fe@Au) Nanoparticles: Synthesis, Characterization, and Magnetic Field-Induced Self-Assembly,” J. Solid State Chem., 159, 26 (2001) and Chen, M. et al, “Gold-coated Iron Nanoparticles for Biomedical Applications,” J. Appl. Phys., Vol. 93, No. 10, 7551 (2003), the complete disclosures of which, in their entireties, are herein incorporated by reference. However, the evidence for Au coating over a magnetic nanoparticle has been inconclusive thus far.
While the conventional structures have provided particle-metal half shell structures via deposition of a thin metal film onto a spherical inorganic/organic polymeric particle, the conventional structures are generally much larger than 30 nm, making them unsuitable for biomedical applications. Moreover, a chemical solution phase has been used to form a structure containing FePt—CdS, CdSe—Au and PdS—CoS. However, there continues to remain a need for the preparation of novel dumbbell-like nanostructures with controlled functionality, which can be used for various nanoelectronic and nanomagnetic applications including various biomedical applications.